1. Field of the Invention
This invention relates to an emission gas purifier carried out by way of catalyst which is in use for exhaust passageway of motor vehicle engine, and particularly concerned to an improved system capable of detecting deteriorating degree of the catalyst.
2. Description of the prior art
In a motor vehicle of recent years, an emission gas purifier is equipped. The purifier has catalyst converter of precious metals such as platinum, palladium and Rhodium through which the emission gas passes. During this process, the toxicant gas such as tri-component of hydrocarbon (HC), carbon monoxide (CO) and nitrogen oxide (NOx) is simultaneously reduced in quantity by the mutual reducing and oxidizing reaction among the toxicant gas components. This purifying system is referred to TTC (Toyota Total Clean System) in Toyota Motor Corporation, and NAPS (Nissan Anti-Air Pollution System) in Nissan Motor Corporation.
With the long use of the motor vehicle, however, the catalyst gradually deteriorates to decrease the purifying effect of the exhaust gas. Consequently, there arises a possibility of continuously runnning the motor vehicle without awaring the deterioration of the catalyst.
Therefore, it is an object of this invention to provide a deterioration detector system for catalyst in use for exhaust gas purifier, capable of making a person aware of whether the catalyst is effective or not with high accuracy, thus preventing a vehicle from being continuously used without replacing the catalyst.
According to the invention, there is provided a deterioration detector system for catalyst in use for emission gas purifier, comprising; an emission passageway through which exhaust gas from internal combustion engine, passes by way of catalyst to facilitate the reducing and oxidizing reaction among the gaseous component of hydrocarbon, carbon monoxide and nitrogen oxide; a sensor placed at said emission passageway to position downstream of said catalyst against the exhaust gas flow so as to generate an output substantially in direct proportion to air-fuel ratio in said exhaust gas; an annunciator arranged to activate in response to the output of more than the predetermined level generated from said sensor.